During rainstorms, water that is not absorbed into the ground runs off into storm-sewer systems for delivery into freshwater systems such as streams, rivers, lakes, and wetlands. While flowing across parking lots, landscaped areas, and other surfaces, the storm-water runoff picks up debris and other pollutants and carries them into the storm-sewer systems. Particularly large amounts of pollutants are picked up at shopping centers with large parking lots, oil-change and auto-repair shops, gas stations, and so forth. These pollutants include motor oil and other hydrocarbons, particulate matter such as sand and grit, and miscellaneous debris such as vegetative matter, paper, plastic, and foam cups. For example, about 200 pounds of miscellaneous debris and 500 pounds of sand and grit is commonly carried off by storm-water runoff from some one-acre parking lots in 90 days.
To maintain freshwater systems, most cities and counties have regulations requiring that some of the pollutants be removed from the storm-water runoff before entering their storm-sewer systems. In order to meet these regulations, facilities typically install on-site pollution traps to filter the storm-water runoff. These pollution traps are sometimes referred to as “oil/grit separators.”
There have been significant advances related to such pollution traps in recent years. These include the innovations disclosed by U.S. Pat. Nos. 6,797,161; 6,936,163; 6,939,461; 6,951,607; 6,994,783; 7,011,743; and 7,037,436, all of which are incorporated herein by reference. While these advances have improved on many of the deficiencies of prior pollution traps, further advances are desired.
For example, maintaining these pollution traps can be difficult due to the space constraints involved. For example, many of these units include filter media deep within a vault/chamber with a 24-inch manhole access, and the filter media must be replaced periodically. The resulting confined-space entry into the vault to replace the filter media is typically a difficult, time-consuming, and unpleasant process.
Accordingly, it can be seen that a need remains for improvements to pollution traps that permit quicker and easier filter-media replacement. It is to the provision of pollution traps meeting these and other needs that the present invention is primarily directed.